feat(modules): 帮助中心、工单、工作流与多渠道接入

补齐 FAQ、帮助中心、工单、可视化工作流及 Telegram/WhatsApp/Slack 等渠道模块。

backend/app/channels/registry.py

@@ -0,0 +1,53 @@
+"""
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
+from typing import Dict, Optional
+
+from app.channels.base import ChannelAdapter
+
+_adapters: Dict[str, ChannelAdapter] = {}
+
+
+def register_adapter(adapter: ChannelAdapter) -> ChannelAdapter:
+    """Register a stateless adapter singleton for its channel_type."""
+    _adapters[adapter.channel_type] = adapter
+    return adapter
+
+
+def get_adapter(channel_type: str) -> Optional[ChannelAdapter]:
+    """Adapter for a channel, or None for channels without one ('web')."""
+    _ensure_loaded()
+    return _adapters.get(channel_type)
+
+
+_loaded = False
+
+
+def _ensure_loaded() -> None:
+    """Import adapter modules on first use (each registers itself).
+    Lazy so importing app.channels never pulls every adapter's deps."""
+    global _loaded
+    if _loaded:
+        return
+    _loaded = True
+    from app.channels import telegram  # noqa: F401
+    from app.channels import whatsapp  # noqa: F401
+    from app.channels import messenger  # noqa: F401
+    from app.channels import instagram  # noqa: F401
+    from app.channels import slack  # noqa: F401
+    from app.channels import email  # noqa: F401
+    from app.channels import sms  # noqa: F401
+    from app.channels import line  # noqa: F401